Thank you for your response! So I guess 'salt' is a bit of a misnomer. What I used to do is this :
1) Say that my key value is something like '1234foobar' 2) I obtain the hash of '1234foobar'. Let's say that's '54824923' 3) I mod the hash by my number of regions. Let's say I have 2000 regions. 54824923 % 2000 = 923 4) I prepend that value to my original key value, so my new key is '923_1234foobar' Is this the same thing you were talking about? A couple questions : * Why would my regions only be 1/2 full? * Why would I only use this for sequential keys? I would think this would give better performance in any situation where I don't need range scans. For example, let's say my key value is a person's last name. That will naturally cluster around certain letters, giving me an uneven distribution. --Jeremy On Sun, May 3, 2015 at 11:46 AM, Michael Segel <[email protected]> wrote: > Yes, don’t use a salt. Salt implies that your seed is orthogonal (read > random) to the base table row key. > You’re better off using a truncated hash (md5 is fastest) so that at least > you can use a single get(). > > Common? > > Only if your row key is mostly sequential. > > Note that even with bucketing, you will still end up with regions only 1/2 > full with the only exception being the last region. > > > On May 1, 2015, at 11:09 AM, jeremy p <[email protected]> > wrote: > > > > Hello all, > > > > I've been out of the HBase world for a while, and I'm just now jumping > back > > in. > > > > As of HBase .94, it was still common to take a hash of your RowKey and > use > > that to "salt" the beginning of your RowKey to obtain an even > distribution > > among your region servers. Is this still a common practice, or is there > a > > better way to do this in HBase 1.0? > > > > --Jeremy > > The opinions expressed here are mine, while they may reflect a cognitive > thought, that is purely accidental. > Use at your own risk. > Michael Segel > michael_segel (AT) hotmail.com > > > > > >
